Salt, acid generator, resist composition and method for producing resist pattern

Abstract

A salt having a group represented by formula (a): wherein X a and X b each independently represent an oxygen atom or a sulfur atom, X 1 represents a divalent group having an alicyclic hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group, and where a hydrogen atom may be replaced by a hydroxy group or a fluorine atom, and * represents a binding site.

What is claimed is: 
     
       1. A salt having a group represented by formula (a2): 
       
         
           
           
               
               
           
         
         wherein X a  and X b  each independently represent an oxygen atom or a sulfur atom, 
         X 1  represents a divalent group having an alicyclic hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group, and where a hydrogen atom contained in the divalent group may be replaced by a hydroxy group or a fluorine atom, 
         ring W represents a C 3  to C 36  alicyclic hydrocarbon group where a methylene group may be replaced by an oxygen atom, a sulfur atom, a carbonyl group or a sulfonyl group and where a hydrogen atom may be replaced by a hydroxy group, a C 1  to C 12  alkyl group, a C 1  to C 12  alkoxy group, a C 3  to C 12  alicyclic hydrocarbon group, a C 6  to C 10  aromatic hydrocarbon group or a combination thereof, 
         L b1  represents a C 1  to C 24  divalent saturated hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group and where a hydrogen atom may be replaced by a fluorine atom or a hydroxy group, and 
         Q 1  and Q 2  independently represent a fluorine atom or a C 1  to C 6  perfluoroalkyl group. 
       
     
     
       2. The salt according to  claim 1 , wherein
 the ring W is a ring represented by formula (a1-1), formula (a1-2) or formula (a1-3: 
 
       
         
           
           
               
               
           
         
         in each of the formulae (a1-1), (a1-2) and (a1-3), a methylene group may be replaced by an oxygen atom, a sulfur atom, a carbonyl group or a sulfonyl group, and a hydrogen atom may be replaced by a hydroxy group, a C 1  to C 12  alkyl group, a C 1  to C 12  alkoxy group, a C 3  to C 12  alicyclic hydrocarbon group, or a C 6  to C 10  aromatic hydrocarbon group. 
       
     
     
       3. The salt according to  claim 1 , wherein
 L b1  is *—CO—O—(CH 2 ) t —, 
 where t represents an integer of 0 to 6, and 
 * represents a binding site to —C(Q 1 )(Q 2 )-. 
 
     
     
       4. The salt according to  claim 1 , wherein
 X 1  is a divalent group represented by formula (X 1 -1), by formula (X 1 -2), by formula (X 1 -3), or by formula (X 1 -4): 
 
       
         
           
           
               
               
           
         
         wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  each independently represent a C 5  to C 12  alicyclic hydrocarbon group where a methylene group may be replaced by an oxygen atom or a carbonyl group and where a hydrogen atom may be replaced by a hydroxy group or a fluorine atom, and 
         * represents a binding site to X a  and X b . 
       
     
     
       5. An acid generator, which comprises the salt according to  claim 1 . 
     
     
       6. A resist composition comprising the acid generator according to  claim 5  and a resin having an acid-labile group. 
     
     
       7. The resist composition according to  claim 6 , further comprising a salt which generates an acid weaker in acidity than an acid generated from the acid generator. 
     
     
       8. A method for producing a resist pattern comprising steps (1) to (5);
 (1) applying the resist composition according to  claim 6  onto a substrate; 
 (2) drying the applied composition to form a composition layer; 
 (3) exposing the composition layer; 
 (4) heating the exposed composition layer, and 
 (5) developing the heated composition layer.